metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White to gray with dark mineral banding; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to gray with dark mineral banding
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to gray with dark mineral banding; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. This recrystallization process causes the quartz grains to interlock, creating an incredibly tough rock.
Uses & applications
Used as road ballast, in construction as crushed stone, for high-end countertops, and occasionally as decorative landscaping stone.
Geological facts
Quartzite is so hard that it will scratch glass. It is often confused with marble, but unlike marble, quartzite will not react with acid (fizz) and is much harder.
Field identification & locations
Identify it by its hardness (it cannot be scratched by a steel nail) and its sugary, crystalline texture that breaks through the grains rather than around them. Commonly found in folded mountain belts globally.
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